1. Field of the Invention
The present invention relates to a cell for preparing competent cells, and in particular relates to a cell which is capable of spontaneously accumulating self-producing trehalose therein and a method for preparing competent cells by using the cell.
2. Description of the Related Art
The process of introducing a DNA molecule carrying a genetic message into a host cell is called “transformation”. Moreover, a host cell which is pre-treated with a physical or chemical treatment and consequently has a property of enabling a DNA molecule to enter therein, easily, is called “competent cells”. In the molecular biology field and genetic engineering operation, in order to enable a host cell to perform a duplication or expression of a specific DNA or protein, obtainment of competent cells which is able to be easily transformed with DNA, is an important and essential process.
Since Escherichia coli cells have advantages of being able to rapidly grow, be cultured easily and be investigated thoroughly, at present, it is a microorganism which is most popularly used as a host cell in many biotechnology related experiments. For recent progress of genetic engineering technology, there have been many methods for preparing Escherichia coli competent cells for the transformation process and transformation, such as the CaCl2 chemical transformation process published by Mandel, M and Higa A. (J. Mol. Biol. 166:557) in 1970 and the transformation process improvements by adding other kinds of cations with different concentrations and an anti-freezing agent into a transformation agent, successively published by Hanahan, D. (J. Mol. Biol. 166:557) in 1983 and by Inoue, H. (Gene 96:23) in 1990. Presently, high transformation process transformation efficiency is 108 transformants/μg plasmid DNA.
However, competent cells which can be transformed, generated from the methods for preparing Escherichia coli competent cells mentioned above, must be stored under a temperature of about −70° C. to −80° C. to prevent an obvious decrease in the transformation efficiency of the competent cells after the competent cells are stored for several months.
In recent years, a technique for preparing relatively stable competent cells at temperature has been developed by Life Technologies Corporation (USA), wherein the competent cells do not have to be stored at a temperature of about −70° C. to −80° C., to hold transformation efficiency of the competent cells stable. The process of the technique comprises adding a specific carbohydrate or chemical polymer to an agent for preparing and storing competent cells as an anti-freezing agent, and thus the competent cells are able to be stored at a higher temperature (such as −20° C.) without obviously reducing the transformation efficiency of the competent cells. Although, compared with the conventional method, the technique saves more energy and the competent cells are transported more easily, the addition of the additional specific anti-freezing agent raises the cost for preparing the competent cells.
Accordingly, a new component and method for preparing competent cells is needed, wherein the competent cell is able to be stored at a higher temperature, to have advantages of saving energy, being of low cost and being able to be transported easily. The new component and method for preparing competent cells, should make the gene transformation technique for organism cells easier.